In a reversible belt tensioner of this type the belt buckle of a vehicle seat belt can be moved by activation of the drive motor. Due to this possibility of movement, the belt tensioner can be used both as a belt buckle feeder when getting into the vehicle and for tensioning the seat belt before or upon collision of the vehicle. By virtue of the reversible design of the belt tensioner it is possible, as a matter of course, to reverse the movement during tensioning or feeding the belt buckle again by an opposite driving direction of the motor.
It is the object of the invention to provide a reversible belt tensioner exhibiting high functional safety and low susceptibility to failure and preferably causing as little operating noise as possible.